1. Field of the Invention
The present invention relates to a CAD/CAM apparatus for inputting a machining shape and machining attributes in an interactive manner on a display device, and for producing NC data for a wire cut electrical discharge machine.
2. Description of the Prior Art
FIG. 1 is a block diagram of a prior art apparatus for producting NC data. Referring to the figure, reference numberal 3a denotes a machining geometric input means for defining elements of a geometric shape to be machined, 3b denotes a machining path generating condition input means for defining the movement of a wire along the defined geometric elements, 3c denotes a machining attribute input means for providing attributes for machining to some geometric elements, 6 denotes a machining information storage means for storing various items of input information, 8 denotes an NC data generation means for analyzing various items of input information to thereby generate NC data, 9 denotes a machining path display means for translating a machining path into a graphic form and displaying it on a display, 10 denotes a CPU, and 11 denotes the display.
FIGS. 2(a) to 2(c) are three-view projections showing an example of a shape to be machined and FIG. 3 is a drawing of the elements to be input from the machining geometric element input means, extracted from the three-view projections (FIG. 2) of the example of a shape to be machined. Referring to FIG. 3, P1 denotes the starting point of machining, L1 denotes a segment as a first element of the shape to be machined with a taper angle of 10.degree., L2 denotes a segment adjoining the segment L1 with a taper angle of 10.degree., L3 denotes a segment adjoining the segment L2 with a taper angle of 5.degree., and L4 denotes a segment adjoining the segment L3 with a taper angle of 5.degree..
FIGS. 4(a), 4(b), and 4(c) are respectively a flow charts for production of the NC data made out by the user according to FIG. 3, a part program, and a machining path drawn on the display. The Steps ST3a, ST3b, ST3c, ST6, ST8 and ST9 in FIG. 4(a) respectively correspond to the means 3a, 3b, 3c, 6, 8 and 9 shown in FIG. 1.
Operation of the apparatus will be described below with reference to the example of the part program shown in FIG. 4(b). Upon receipt of the machining drawing (FIG. 2 , the operator assigns arbitrary names (numerals) to necessary elements in the drawing (P1, L1-L4, in FIG. 3) and defines the information which these elements have in a machining geometric element input step ST3a. This operation corresponds to lines 0001 to 0005. Line number 0001 indicates that X coordinate and Y coordinate of the machining starting point P1 are both 0's. Line number 0002 corresponds to the first machining element of the shape approached from the machining starting point P1 and indicates that it is a segment with Y coordinate being 10, line number 0003 indicates a segment with X coordinate being -40, line number 0004 indicates a segment with Y coordinate being 60, and line 0005 indicates a segment with X coordinate being 20.
Then, definition of the movement and definition of attributes are respectively performed in a machining path generating condition input step ST3b and in a machining attribute input step ST3c. These operations correspond to line number 0006 and onward. Line number 0006 is an instruction for establishment of the coordinate system, specification of the offset direction, and assignment of the offset number, where it is indicated that the current position is set to the coordinate P1, the offset direction is left, and the offset number is 1. Line number 0007, 0012, and 0016 specifies the taper angles, each of which affects the following elements until another taper angle being newly specified. In numerical control apparatuses, in general, the specification for the direction of inclination of the taper is made by giving a minus sign "-" to the value when it is inclined to the left with respect to the advancing direction and by giving a plus sign "+" (this sign can be omitted) when it is inclined to the right. The same rule is applied to the present example. Line numbers 0008, 0010, 0013, 0014, 0017, 0018, and 0021 indicate the paths along which the wire moves by using the names of geometric elements, where PO denotes the origin (0,0) of the coordinate system, and LY denotes the y-axis. Line number 0009 is an instruction that the corner portion between the geometric elements in the paths of movement indicated in the preceding and following steps should be connected with an arc of a specified radius. Each of line numbers 0011 and 0015 is an instruction, in addition to the instruction for the corner arc as described above with reference to line number 0009, of the radius of the corner arc of an auxiliary plane to that corner arc, that is, for corner radii assignment to both upper and lower planes. At this time, the elements in continuance with the corner arc must be segments. The height of the auxiliary plane is set in the numerical control apparatus. Line number 0019 indicates an instruction word for outputting M01 of NC data, line 0020 indicates an instruction word for causing NC data to be directly output, and line 0022 indicates the end of the part program.
Since the prior art CAD/CAM apparatus is constituted as described above, troublesome operations should be performed in entering additional machining attributes for producing NC data. For example, the taper angle must be input in consideration for the direction of the inclination after deciding the advancing direction of the machining. Even if only the advancing direction of the same machining shape is to be, changed the definition must be made over again, thus deteriorating the throughput efficiency. Further, there have been problems that it is difficult to confirm the additional information corresponding to the machining attributes, and hence it takes a long time to input data from a keyboard, and in addition complicated instruction words must be learned.